The females of this medium-sized hard shell turtle grow to a much larger size than males. Females reach a maximum of 25cm (9.8 in) while males reach only 14cm (5.5 in). Coloration is highly variable, although adult terrapin carapaces (top shells) are generally a shade of grey with lighter colored concentric rings (circles inside of circles). Heads and limbs are also a shade of grey, with variable spots or blotches. Orange rings with a grey or greenish background may appear on shells, but there is a wide variety of patterns and colors in the species, sometimes even within single populations. Feet are webbed for strong swimming.

Habitat

The diamondback terrapin is found in brackish (water with some salinity) coastal waters. Typical habitats include coastal swamps, estuaries, lagoons, tidal creeks, mangrove thickets, and salt marshes. Although the species is found in brackish water, periodic access to freshwater is necessary for health.

Distribution

The diamondback terrapin is native to Alabama, Connecticut, Delaware, Florida, Georgia, Louisiana, Maryland, Massachusetts, Mississippi, New Jersey, New York, North Carolina, Rhode Island, South Carolina, Texas, and Virginia, occurring along brackish coastal waters of the Atlantic Ocean and the Gulf of Mexico, from Cape Cod, Massachusetts, in the north, to Corpus Christi, Texas, in the south. A small breeding subpopulation is also found in Bermuda (United Kingdom).

Threats

Diamondback terrapins are currently collected for pets as the long-term historical trend of commercial harvest for meat (for the soup trade) has declined. Terrapin stew was a popular delicacy in the United States and Diamondback terrapins were exported in large quantities to several European countries. In the late 19th century 400,000 pounds of turtle were harvested annually. By 1920, Diamondback terrapin populations had dwindled, and only 823 pounds were harvested that year on the Chesapeake Bay, selling for $125 per dozen. Prohibition (sherry was a main ingredient in soup) and the Great Depression in the United States helped reduce demand for Diamondback terrapins. This allowed the population to slowly recover. Although most states now have legislation that regulates the collection of Diamondback terrapins, this species is still taken from the wild in parts of its range. In 2006, the last year in which this species was legally harvested in Maryland, watermen reported a catch of 10,500 Diamondback terrapins.

Exports of this species from the United States have increased from under 1,000 turtles per year in 1999 to 3,000 turtles per year by 2010, with a high of 6,000 turtles exported in the year 2006. Asian countries began importing Diamondback terrapins and other U.S. species due to the depletion of most of their native turtle species, with some vendors selling as many as 2,000-3,000 of these turtles in a single year. It appears that the species is used both in the pet and the food and medicinal trades. The demand for Diamondback terrapins from Asian markets was one of the major reasons that led to the permanent closure of the terrapin fishery in Maryland in April 2007. Several other U.S. states, however, still allow commercial harvest of terrapins.

Declines in populations are now mostly associated with increased anthropogenic (human) activity, usually turtle drowning from the use of crab pots, but also habitat loss and commercial harvest. Diamondback terrapin populations have been heavily affected by urbanization across their entire range. Increased sediments and sewage in waterways, pollutants, diking, dredging, filling of salt marshes, and the development and maintenance of shipping channels all pose significant threats to terrapin habitat. Coastal development is particularly problematic because it frequently destroys nesting beaches. Predicted sea-level rise would be a particularly severe impact on terrapin marshland and nesting habitat. In states with a commercial blue crab fishery, incidental drowning in crab pots is considered to be the major threat to the Diamondback terrapin.

Adult female Diamondback terrapins are frequently killed by motor vehicles while attempting to cross motorways in search of nesting sites. Human-subsidized predators--native or introduced animals whose populations prosper as a result of association with humans and human-altered habitats (i.e. raccoons)-- are another threat to diamondback terrapin populations. Studies in New York identified raccoons and Norway rats as major predators on the adults, juveniles, and eggs of the terrapin.

Additional Information

Read the proposal submitted by the United States for consideration at CoP16.